class Solution {
    int dx[8] = { 0, 0, 1, -1, -1, -1, 1, 1 };
    int dy[8] = { 1, -1, 0, 0, 1, -1, 1, -1 };
    int m, n;
    void dfs(vector<vector<char>>& board, int i, int j)
    {
        // 判断周围地雷个数
        int mine = 0;
        for(int k = 0; k < 8; k++)
        {
            int x = i + dx[k], y = j + dy[k];
            if(x >= 0 && x < m && y >= 0 && y < n && board[x][y] == 'M')
                mine++;
        }

        if(mine == 0)
        {
            // 没有地雷，则递归展开
            board[i][j] = 'B';
            for(int k = 0; k < 8; k++)
            {
                int x = i + dx[k], y = j + dy[k];
                if(x >= 0 && x < m && y >= 0 && y < n && board[x][y] == 'E')
                {
                    dfs(board, x, y);
                }
            }
        }
        else
        {
            // 有地雷
            board[i][j] = mine + '0';
        }
    }
public:
    vector<vector<char>> updateBoard(vector<vector<char>>& board, vector<int>& click) {
        m = board.size(), n = board[0].size();
        if(board[click[0]][click[1]] == 'M')
            board[click[0]][click[1]] = 'X';
        else
            dfs(board, click[0], click[1]);
        return board;
    }
};